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    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
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    <script>
      console.log("" + 1 + 0); //"10"
      console.log("" - 1 + 0); //-1
      console.log(true + false); //1
      console.log(6 / "3"); //2
      console.log("2" * "3"); //6
      console.log(4 + 5 + "px"); //"9px"
      console.log("$" + 4 + 5); //"$45"
      console.log("4" - 2); // 4
      console.log("4px" - 2); //NaN
      console.log(7 / 0); //Infinity
      console.log("  -9  " + 5); //"  -9  5"
      console.log("  -9  " - 5); //-14
      console.log(null + 1); //1
      console.log(undefined + 1); //NaN
      console.log(" \t \n" - 2); //-2 看不见的字符转0
    </script>
  </body>
</html>
